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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package io.netty.channel;
  
  import io.netty.util.concurrent.Future;
  import io.netty.util.concurrent.GenericFutureListener;
  
  
  /**
   * Listens to the result of a {@link ChannelFuture}.  The result of the
   * asynchronous {@link Channel} I/O operation is notified once this listener
   * is added by calling {@link ChannelFuture#addListener(GenericFutureListener)}.
   *
   * <h3>Return the control to the caller quickly</h3>
   *
   * {@link #operationComplete(Future)} is directly called by an I/O
   * thread.  Therefore, performing a time consuming task or a blocking operation
   * in the handler method can cause an unexpected pause during I/O.  If you need
   * to perform a blocking operation on I/O completion, try to execute the
   * operation in a different thread using a thread pool.
   */
  public interface ChannelFutureListener extends GenericFutureListener<ChannelFuture> {
  
      /**
       * A {@link ChannelFutureListener} that closes the {@link Channel} which is
       * associated with the specified {@link ChannelFuture}.
       */
      ChannelFutureListener CLOSE = new ChannelFutureListener() {
          @Override
          public void operationComplete(ChannelFuture future) {
              future.channel().close();
          }
      };
  
      /**
       * A {@link ChannelFutureListener} that closes the {@link Channel} when the
       * operation ended up with a failure or cancellation rather than a success.
       */
      ChannelFutureListener CLOSE_ON_FAILURE = new ChannelFutureListener() {
          @Override
          public void operationComplete(ChannelFuture future) {
              if (!future.isSuccess()) {
                  future.channel().close();
              }
          }
      };
  
      /**
       * A {@link ChannelFutureListener} that forwards the {@link Throwable} of the {@link ChannelFuture} into the
       * {@link ChannelPipeline}. This mimics the old behavior of Netty 3.
       */
      ChannelFutureListener FIRE_EXCEPTION_ON_FAILURE = new ChannelFutureListener() {
          @Override
          public void operationComplete(ChannelFuture future) {
              if (!future.isSuccess()) {
                  future.channel().pipeline().fireExceptionCaught(future.cause());
              }
          }
      };
  
      // Just a type alias
  }